Enlightenment is a state beings can achieve in many ways, such as touching a S P A G O O T, acquiring the Octahedron of Transcendence, and becoming Angery. It is also possible to achieve Enlightenment as a reward of heroism from the Council of the Ancients.
When a being is in this state, their eyes glow brightly with a white light. It supposedly signifies that the being in the state in significantly more powerful that usual. The power of an enlightened far surpasses even a Transcendent.
At the end of ROTR 2, after the defeat of the Omniscronchulon, Meme Man was awarded by the Council with Enlightenment for his heroism.